Wind turbines have become an important source of electrical power worldwide. Generally, wind turbines are supported by a tower and driven by multiple wind turbine blades, each of which is typically tens of meters in length. As efforts are made to increase the amount of electrical power generated per wind turbine, the length of the wind turbine blades has also correspondingly increased.
The significant length of currently available wind turbine blades, as well as the continuing efforts to design and manufacture even longer wind turbine blades, has presented substantial challenges for those tasked with transporting wind turbine blades along the entire route from the manufacturer, through any seaports, and across country to the wind turbine farms. One particular challenging scenario is the transportation of such significantly long objects by rail.
To prevent collisions with objects in the area surrounding a railroad track, the railroads and regulatory authorities have established clearance envelopes defining the maximum distance an object can extend laterally and vertically from a railcar. The clearance envelope is typically route dependent and commonly accounts for such variables as the degree of curvature in the curves, fixed obstructions along the right-of-way (e.g., waysides, signs, and signals), track irregularities, and the type of equipment being used.
In the case of wind turbine blades, which are normally transported on one or more standard flatcars, the clearance envelope dictates the maximum swing-out the tip and/or root of the blade can extend laterally beyond the side of the supporting flatcar when the train traverses a curve. As wind turbine blades become increasingly longer, the ability to keep swing-out within the clearance envelope during rail transport becomes correspondingly more difficult. In addition to having to take into account the curvature of the curves the train is expected to encounter, a number of other variables must be considered when attempting maintain swing-out within the clearance envelope, such as vertical differences between cars as they transverse vertical slopes, the action of the couplings, and the flexing of the blade due to wind. In addition to maintaining swing-out within the clearance envelope, the structures supporting the blade on the railcars must also minimize the chance of blade damage, such as gel cracking of the shell.